a:4:{i:0;s:3:"uid";i:1;s:8:"group_id";s:3:"_pk";a:2:{i:0;s:3:"uid";i:1;s:8:"group_id";}s:5:"_type";a:2:{s:3:"uid";s:16:"int(11) unsigned";s:8:"group_id";s:16:"int(11) unsigned";}}